1. Field of the Invention
The present invention relates to testing processes for toxicity involving microorganisms and more particularly to testing processes for toxicity involving bioluminescent organisms.
2. Description of the Prior Art
The present known method of testing oil well drilling fluids for toxicity is prescribed by the Environmental Protection Agency (E. P. A.) as published in 50 Federal Register 34592-01, Appendix 3. This method employs the mysid shrimp (Mysidopsis bahia) as the assay organism. Equal sized groups of shrimp are placed in holding containers. One group, the control, receives no treatment while the other containers receive dilutions of the test samples of oil well drilling fluids. After 96 hours, dead and living shrimp are counted and the median lethal concentration, LC-50, calculated as that concentration of drilling fluid that results in the mortality of 50 percent of the test organisms. The shrimp are difficult to raise and handle as laboratory assay organisms. This method is labor intensive, because it requires a long assay time (about 96 hours) and because the mysid shrimp are extremely sensitive to changes in laboratory conditions, the process sometimes requires repeated assays and has a coefficient of variation of 20 to 40 percent.